Sandwich-type building panels are known having a pair of relatively dense skins between which is enclosed a foamed synthetic-resin mass with open and closed cells. The mass can be made of polystyrene, polyurethane, polyisocyanate, polyvinylchloride, and the like. This mass is usually installed as a plate of hard material between the outer skins or is injected therebetween and allowed to foam and harden. It is common practice to stiffen the edges of such panels by means of hard shythetic-resin, wood, or metal edge members.
Such sandwich panels are well known for use in windows and door frames. However, their use on a large scale as construction elements for partition walls and the like in buildings has been impossible. This is due to the fact that such panels are very difficult to anchor securely in place in a conventional building. It is necessary to provide frames to support such panels so that their main advantages are lost in the added construction costs and, indeed, in the often unattractive appearance of such frames.
In addition there is a considerable difficulty with such panels in that they are rapidly destroyed in case of fire. Even when the skins are made of relatively fireproof and rupture-proof material the panel is able to withstand only a small amount of heat before it is completely destroyed. This is due to the fact that the foamed synthetic-resin mass between these skins generates considerable gas when heated. The pressure of this gas builds up between the skins and frequently blows them explosively apart, thereby completely destroying the panel and allowing the fire to pass readily into the next room. Once the fire has reached the foamed mass between the skins the panel is very quickly destroyed. This is particularly true where the core material when molten is flammable as then the entire panel will burst into flames. Thus such panels not only are ineffective for limiting and preventing fires, but frequently in themselves can create a fire hazard. For this reason most building codes completely prohibit the use of such panels on any large scale.